Ants

Among the many substances identified in ants as pheromones or allomones, one group of offensive compounds is worth mentioning. Crematogaster ants are a large, aggressive, world-wide genus. They have the unusual ability to bring their abdomens forward over their heads and place a toxic secretion on other insects with their flattened sting. Some of the European species store long-chain unsaturated keto-acetates, of the form shown in Figure 3.34, in their Dufour glands (part of the poison apparatus). These are ejected with enzymes from the poison gland (an acetate esterase and an alcohol oxidase) to hydrolyze the acetates and

Figure 3.34 Examples of the substances stored in the Dufour gland by Crematogaster scutellaris ants. On ejection they are hydrolyzed to alcohols and then oxidized to aldehydes, the true offensive compounds, by enzymes from the poison glands

Figure 3.34 Examples of the substances stored in the Dufour gland by Crematogaster scutellaris ants. On ejection they are hydrolyzed to alcohols and then oxidized to aldehydes, the true offensive compounds, by enzymes from the poison glands oxidize the alcohols to aldehydes. These unsaturated keto-aldehydes are strong electrophiles, reacting with OH, SH and NH2 groups, and are strongly toxic to other ants. The biosynthesis of the acetates has not yet been studied but would appear to be from oleic and palmitic acids with chain extension by an unknown C5 fragment.